Method and apparatus for electrical prospecting



Dec. 1, 1936. T, ZUSCHLAG 2,062,630

METHOD AND APPARATUS FOR ELECTRICAL PROSPEGTING Filed May- 5, 1954 lNV-ENTOR G "M 5. A TTORNE 6' v Patented Dec. 1, 1936 t c UNITED STATES PATENT OFFICE,"

METHOD AND APPARATUS FOR ELECTRICAL PROSPECTING Theodor Zuschiag, West Englewood, N. J., as-' signor to Hans T. F. Lundberg, New York,

application my a, 1934,8Q1'i81N0. 723,669 15 Claims. (or 175-182) This invention relates to electrical prospecting, l and II respectively; and the said electrodes 4 and has for an object to provide an improved and 6 are also connected in series by a two pole, method and apparatus for the determination of double throw reversing switch |2;'a three pole, ground potential and electromagnetic'field ratios double throw reversing switch l3, and an adjustfor the purpose of aiding in predetermining the able resistance M, to the ends of the potentiom- 40 A suitable source of power, such as a buzzer or center pole of switch 25 location, character, quantity, and quality of deeter I 5.

posits. Switch l3 serves to connect resistance It with Another object consists in providing method potentiometer l5 and either electrode 4 or elecand apparatus which have a greater range of aptrode 6.

plication than those heretofore known, and which A multiplier resistance 30 is arranged to be 1o embody a simpler and more accurate mode of connected in series with potentiometer l5 by operation as well as simpler and more rugged means of the multiplier switch 3|, in order to extype of construction. tend the range of the said potentiometer.

Another object consists inthe provision of a The secondaries I 6 and I? of transformers i0 transformer coupled potentiometer combination and II, respectively, are connected in series by a 1-5 useful in effecting the balancing or compensation condenser l8 to the potentiometer net-work l9,

and apparatus; whereby the range of application and 2|; which potentiometer 2| includes two is materially enhanced. fixed, electrically equal resistances 22 and 23.

20 Another object consists in the provision of a "The combination 2|, 22, and 23 is shunted across 20 potentiometer in substitution for two mdependpotentiometer. '20. The value of condenser I8 ent resistances, whereby the construction and should be suchthat, for a given frequency of theoperation are materially simplified. power source I, it'sreactance equals the induct- Another object consists in providing improveance of the secondaries I 6 and H, in order to 25 ments leading to more accurate results attainable eliminate any undesirable, phase variations in 25 iliary instruments or acquiring knowledge 01' adthe potentiometer combination 2!, 22, and 23,

ditional data. I thereby ensuring the same amount of current A further object consists in providing certain flow in the two pctentiometers 20 and 2!. 3o improvements in the form, construction and ar- The central pickp electrode 5 is connected rangement of the several parts, in the elements by the two pole, double throw selector switch 24 jects may effectively be attained. 25 and, when this switch is thrown to the left in 35 A practical embodiment of the apparatus subthe drawing, the center-tap of potentiometer 20 ject matter of my invention is diagrammatically is connected in series by an amplifying device 26 represented in the accompanying drawing to to the righthand end of potentiometer l5, which which reference will now be made. latter, at the same time, is short-circuited by the rent generated by the power source and flowing ground area between and surrounding the electrodes. Within this energized area I- locate three picktiometer is opened with the result that the line at arbitrary space intervals circuit is thus established, which consists of up electrodes denoted by 4, 5 6, which said elecpreviously obtained balance of the 'k is Electrodes 4 and 6 are connected by means of the slider potentiometer connected a, two pole double throw selector switch, marked h the amplifier 25 o the i r 0f Do h 1, in series with primaries8 and 9 of transformers eter 2|. the center-tap or which latter is contiom I Q of turns of insulated nected to the center-tap of potentiometer 24. In this condition the network. may again be brought to a condition of balance by adjusting the sliders of the two potentiometers i8 and 2|.

By placing slider switch 24 in its center position, the connection with center-electrode i will be opened, and the sliders of potentiometer and resistance l4 will be connected with a pickup coil 28. By reversing selector switch I, the network will be separated from pick-up electrodes 4 and 4 and connected to a pick-up coil 29. The said two pick-up coils 2t and .2! may be composed, for instance, of a suitable number copper wire with a diameter of, say, from one to two feet.

Finally, if the selector switch 24 is thrown to the extreme right in the drawing, the pick-up coil 28 will be cut off from the network and its place be taken by the two electrodes 5 and I.

pick-up coil 28 and By the use of this arrangement of apparatus it is possible to measure the following quantities:

1. The potential drop ratio between the electrodes 4, 5 and 5, I.

2. The electro-motive force-potential drop ratie between the electro-motive force induced in the potential drop between electrodes 4, 8.

3. The electro-motive force potential drop ratio between the pick-up coil 24 and electrodes 4, 8 and the potential drop-electro-motive force ratio of the potential drop between electrodes 4, 4 and the electro-motive force induced in pick-up coil 29.

In order to measure the potential drop ratio, selector switch 1 must be connected to the outer electrodes 4 and 4, while selector switch 24 is connected to the center electrode 5. neversins switch l2 may be connected either way, two position switch 25 should be moved to the left in the drawing. The network is then balanced by operating the three pole switch andthe i2, and adjusting the sliders of resistance l4- and potentiometer 20 until zero deflection is obtained on the'indicator 21. The thus obtained balance is then upset by moving switch 2! to its righthand position in the drawing, whereupon a new balance may be established by adjusting the sliders of potentiometers i5 and 2|, after operation of multiplier switch-2| if necessary. but

without touching any of the 'prior adjustments. The resultant settings of the potentiometers I! and 2| are then indicative of the unknown potential drop ratio, and the numerical values of the settings may be used to calculate this ratio by well known mathematical prwedura In order to measure the ratio between the electrc-motive force and the potential drop between electrodes 4, 8, selector switch 'I must be connected to the outer electrodes 4 and 8, and selector switch 24 to the pick-up coil 22. The three pole switch 25 is then returned to its lefthand position, and the network is balanced by suitably operating reversing switches i2 and II and adjusting the sliders of resistance and potentiometer 20 till zero deflection is obtained on indicator 21. its rishthand balance re-established by adjusting the sliders of.potentiometers I! and 2| without altering the prior adjustments. The resultant settings of potentiometer-s i5 and 2i are again indicative of the unknown electro-motive force-potential drop ratio, and the numerical value of this ratio may be calculated from the osition, and the transformer coupled 'up coil 29, and selector switch 24 to pick-up coil 28. Switch 25 is then returned to its lefthand position, and the measuring operation as just described for the electro-motive.force-potential drop ratio, is repeated.

Finally, in order to measure the ratio of the potential drop between stakes 4, 6 and the electromotive force induced in pick-up coil 29, selector switch I is connected to pick-up coil 29, and selector switch 24 to electrodes 4 and 6. Switch 25 is then moved to the lefthand position, and the measuring operation as described for the electromotive force-potential drop ratio, is repeated.

It will be observed that all four of the measuring combinations hereinbefore set forth utilize the same measuring procedure, which consists of two successive balancing operations, each involving two different adjustments. The two adjustments for each balancing operation serve to take care of the two variables which are characteristic of alternating current measurements to wit, amplitude and phase or in-phase and out-of-phase components. Generally speaking, one adjustment takes care of the in-phase and the other of the out-of-phase component, encountered in the electrical prospecting investigations. The two successive balancing operations are effective to eliminate such ground and instrumentresistances drawing, let switches l2 and i3 be set to the right,

and switch 25 to the left. The potential between electrodes 4 and 8 will then cause a current to flow in the circuit composed of the elements indicated by the reference numerals 4, 1, 8, l2, I3, 25, l3, l4, l2, l2, 8, I, i (25 being short-circuited). The central electrode 5 is connected with this circuit through the indicator branch circuit composed of the elements marked 24, 20, 25, 26, and 25. When in balanced position, no current is flowing through this indicator balanced position may be realized by adjusting resistance l4 and potentiometer 20 until there is zero deflection of indicator 21. The function of resistance I4 is to compensate the network not only for unequal potential drop between-electrodes 4, 5 and 5, 6, but also to compensate for the various contact and instrument resistances present in the outer electrode circuit. When using alternating current, the adjustment of the resistance i4 alone is not, effect a complete neutralization of the network; and, in order to obtain such a condition of neutralization, it is necessary to provide for a separate compensation of the out-of-phase components that are still present in the indicator circuit. This may be accomplished by the use of the potentiometer combination l6, l1, ll, and is, which provides a substantially ninety degrees out-of-phase component, the exact phase displacement of which depends upon to the object of the various branch, and said however, sufficient to I the mutual relationship between the reactance of v where i1 is the now resultant 2,062,680 3 tentialdrops E45 and E56 between stakes l, I and by the insertion of potentiometer l5, therefore I, 6, are set forth by the following equations: Equations 6 and 7 may be written:

where n is the current flowing in the outer stake circuit i: is the current in the secondaries of transformers i2o=i2/2 the current flowing in potentiometer 20 ,i

R4 is the contact resistance at stake 4 Re is the contact resistance at stake 6 R14 is the value of resistance ll fa is the impedance of primary 8 go is the impedance of primary 9 mm is the former l mu is the mutual inductance of transformer ll v P20 is the resistance between the slider and center-taper potentiometer 20 f is the frequency of the alternating curre- 9' and w are two well known mathematical ymbols. r The relation between the currents i1 and 4': is given by the equation: (3) i=-4ci1 where C is an instrument constant and equals:

K m-F u) I k 1c+ 17+Z1a+ 19.

In this expression:

(is, m are' the impedances of the secondaries l6 and I! v (is is the reactance of condenser l8 R19 is the resultant resistance of potentiometer combination l9 Substituting the value of i: as given by Equation 3 in Equations 1 and 2, the following new equations obtain:

current flow in the outer stake circuit i2 is the now resultant current in the secondaries of transformers iz1=izo='i2'/2 is the now,resultant current in potentiometers 20 and 2i P15 is the resistance between the right end and the slider of potentiometer l R15 is the total resistance of potentiometer l5 P21 is the resistance between the slider and center-tap of potentiometer 2|.

The instruments factors C and C are not afiected mutual inductance, of trans- Now, dividing Equation 4 by Equation 5 and Equation 8 by Equation 9,

i1 and i1 cancel each other.

() I Ea E50 R PI5+J'C'P21 The only unknown strument constant C. In many cases the nu-. merical value of the product C'Pzr is small and Whenever may be written in the E45 P15 (11) 5d i1s 1s If. on the other hand, the value of C'Pzr is not a negligible factor but must be taken into consideration, then the value of C The same formulae apply to the other types of goo-electric investigations to which this appa ratus is adapted.

tious predetermination of valuable data concerning desirable sub-surface deposits, in spite of the presence of substances tending to inhibit or hinder ,such predetermination.

It will be understood that various changes may lowed in carrying out the method; as well as in the order of the said steps; without departing from the spirit and scope of my invention: and

the two current values factor remaining is the inhence I do not intend to be limited to the details herein shown and described, except as they may be included in the claims.

What I claim is:

1. In a method 0! electrical prospecting, the steps of establishing an electric ground field in a tract to be investigated, producing in a measuring network having a plurality of branches current flow due to the character 01 said ground field, balancing the current in said network by procedure including the adjustment of a-potentiometer to compensate for phase displacement between difierent branches oi said network, altering the curre t now in said network, .and reestablishing the balance of said network. 7

2. In a method oi! electrical prospecting, the

steps of establishing an electric ground fieldin a tract to be investigated, producing in a measuring network having a plurality of branches current flow due to the characteroi said ground field, balancing the current in said network by procedure including the adjustment or avariable resistance to compensate for difference in magnitude between difierent branches 0! said network, and the adjustment'oi a potentiometer to compensate for phase I I cut branches, altering the current fiow in said network, and re-establishing the balance of said network.

3. In a method of electrical prospecting, the steps of establishing an electric ground field in a tract to be investigated, producing in a measuring network having a plurality of branches cur rent flow due to the character oi said ground field,

balancing the current in said network by procedure including the adjustment of a potentiometer inductively coupled with said network "to for phase displacement between ditferent branches or said network. altering the current flow in said network and re-establishing the balance of said network.

Gil

4. In a method 0! electrical prospecting, the steps of establishing an electric ground field in a tract to be investigated, producing in a measuring network a current flow due to the character of said ground field, balancing the current in said network by means including a potentiometer, altering the current fiow in said network by means including a'second'potentiometer, and re-establishing the balance of said network.-

5. In a method a: electrical prospecting, the steps of establishing an electric ground field in a tract to be investigated, producing in'a measuring network a current fiow due to the character of said ground field, balancing the current in said network by means including a potentiometer, al-

tering the current flow in said network by means including a second potentiometer inserted into said ground field, balancing the current in said network by means including a potentiometer, al-

tering the current fiow in said network by means including a second potentiometer, and re-establishing the balance or said network by means including a third potentiometer.

'1. Ina method of electrical prospectlns, the steps of establishing an electric ground field in a tract to be investigated, producing in a measuring network a current fiow due to'the character of said ground-field, balancing the current in said displacement between said diflerexisting in difierent existing in diiIerent network by means includinga potentiometer, altering the current fiow in said network by means including a second potentiometer, and re-establishing the balance 01 said network by means including agthird potentiometer connectcdin series parallel combination with said first potentiometer.

8. In a method of electrical prospecting, the steps of establishing an electric ground field in a tract to be investigated, producing in a measuring network a current flow due to the character of said ground field, balancing the current in said network by means including a potentiometer, altering the current flow in said network by means including a second potentiometer, re-establishing the balance of. said network by means including a third potentiometer and noting the settings of the said second and third potentiometers resulting from the re-establishing of the balance of said network.

9. In a method of electrical prospecting, the

tering the current flow in said network by means including a second potentiometer, re-establishing the balance of said network by means including a third potentiometer connected in series parallel combination with said first potentiometer and noting the settings 0! the said second and third potentiometers resulting from the re-establishing of the balance of said network.

10. In an apparatus for electrical prospecting including means for establishing an electric groundfield and a measuring network adapted for the generation therein of a current fiow due to the character of the ground field, means for determining the ratio of the electromotive forces existing in different parts of said ground field comprising, the combination of a balancing net- ,workand an. indicator circuit, said network including at least one potentiometer for the purpose of deter-mini the numerical value or the ratio and said circuit-including at least one potentiometer'ior the purpose of compensating phase l1. In an apparatus ior electrical prospecting including means for establishing an electric ground field and a measuring network adapted for the generation thereinot a current fiow due to the character oi'the ground field, means for determining the ratio of the electromotive forces I parts of saidground field comprising, the combination of a balancing network and an indicator circuit, said network ineluding at least one variable resistance and at least one potentiometer for the purpose or determining the numerical value ofthe said ratio and said circuit including at least one potentiometer for the purpose of compensating phase displacement between the electromotive forces.

12. In an apparatus for electrical prospecting including means ior T establishing an electric groundfield and a measuring network adapted.

for the generation therein oi a current flow due to the characterof the ground field, means for determining the ratio oi'the electromotive forces 7 parts of 'said ground field comprising, the combination of a balancing network and an'indicator circuit, said network including at least one potentiometer for the purpose of determining the numerical v value of the said ratio and said circuit including two potentiome- ;7

ters for the purpose of compensating phase'displacement between the electromotive forces.

13; In an apparatus for electrical prospecting including means for ground field and a measuring network adapted for the generation therein of a current flowidue to the character of the comprising, the combinatlon of a balancing network and an indicator circuit, said network including at least one variable resistance and at least one potentiometer for the purpose of determining the numerical value of the said ratio and said circuit including two potentiometers for the purpose of compensating phase displacement between the electromotive forces.

14. In an apparatus for electrical prospecting including ,means for establishing an electric ground field and a measuring network adapted for the generation therein of a current flow due to the character of the ground field, means for determining the ratio of the electromotive forces existing in difierent parts of said ground field comprising, the combination of a balancing network and an indicator circuit, said network intwo potentiometers.

15. In an apparatus for electrical prospecting including means for establishing an electric ground field and a 'measuring, network adapted for the generation therein of a current flow due to the character of the ground field, means for determining the ratio of the electromotive forces existing in difierent parts of said ground field comprising, the combination of a balancing network and an indicator circuit, said network including at least onevariable resistance and at least one potentiometer for the purpose of determining the numerical value of the said ratio. said tween the electromotive forces, and means to adjust the phase of the current flowing in said last named two potentiometers.

THEODOR ZUSCHLAG. 

